NEW KNOWLEDGE ABOUT POLYAMIDE FILAMENT DYEING WITH ANIONIC DYE

Abstract

The new knowledge through a concrete scientific study of the dyeing process of polyamide filament yarns (nylon yarn) with anionic dye in slightly acidic medium without any other additives (electrolyte, yeast, equalizer, etc.) in order to transfer the process in industrial conditions have investigated in this study. Generally, polyamide fibers (nylon, PA) have a different but similar chemical composition, depending on the base materials used for their synthesis. Anionic dye is usually used for dyeing cellulosic materials, but in special cases it can also be used for dyeing other textile raw materials. In this study, samples of polyamide filament yarn of linear density of 151 Nm have dyed with anionic dye at a temperature of 95 °C. Acetic acid was added in the dyeing solution to adjust the pH of the medium. The used dye is marked like C.I. Direct Red 1. The used dye concentrations for dyeing the samples were 5, 10, 15 and 20 mg/dm3, while the time of the dyeing process were 5, 10, 15, 25 and 40 minutes. At the end of dyeing, the absorbance measuring at the maximum wavelength (520 nm) was performed using a spectrophotometer (Cary 100 Conc UV-VIS, Varian). From the results, the degree of exhaustion dye and the amount adsorbed dye are obtained. The degree of dye exhaustion compared to initial dye concentration for different dyeing time, after 40 min was 70 %. The influence of the contact length between adsorbate (dye) and absorbent (polyamide yarn) on dye is evident i.e. a longer time contributes to a bigger degree of exhaustion. Changing the adsorbed amount of adsorbate on the adsorbent for different initial concentrations and dyeing time shows continuity in changes during initial concentration and time growth, i.e. a bigger amount of dye in the solution or longer dyeing time cause a bigger amount of adsorbed dye per unit mass of the adsorbent. Isotherms of adsorption are of big importance for the study of the dyeing process, so more of them were used in this study, but thee isothermal Halsey model was the most effective for clarifying process of dyeing. High functionality of the variables was detected with Halsey model (coefficient of determination=0,995). The process of dyeing polyamides with used dye solves the problem of large quantities of electrolytes and surfactants in wastewater after dyeing. The results show that the addition of acetic acid in solution, gives a bigger dye adsorption to the fiber. For better results, it is necessary to carefully select to the appropriate of the bath (appropriate acid, mineral-organic, some additives, etc.), the temperature-time regime od dyeing process, as well as the dyeing stage itself. For better results, it is necessary to carefully select the appropriate composition of the bath (appropriate acid, mineral-organic, some additives, etc.), the temperature-time regime of the dyeing process, as well as the dyeing phase.